added experimental improved Perlin noise shader

experimental/SkPerlinNoiseShader2/SkPerlinNoiseShader2.h

 /*
  * Copyright 2013 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
-#ifndef SkPerlinNoiseShader_DEFINED
-#define SkPerlinNoiseShader_DEFINED
+#ifndef SkPerlinNoiseShader2_DEFINED
+#define SkPerlinNoiseShader2_DEFINED
 
 #include "SkShader.h"
 
-/** \class SkPerlinNoiseShader
+/** \class SkPerlinNoiseShader2
 
-    SkPerlinNoiseShader creates an image using the Perlin turbulence function.
+    SkPerlinNoiseShader2 creates an image using the Perlin turbulence function.
 
     It can produce tileable noise if asked to stitch tiles and provided a tile size.
     In order to fill a large area with repeating noise, set the stitchTiles flag to
     true, and render exactly a single tile of noise. Without this flag, the result
     will contain visible seams between tiles.
 
     The algorithm used is described here :
     http://www.w3.org/TR/SVG/filters.html#feTurbulenceElement
 */
-class SK_API SkPerlinNoiseShader : public SkShader {
+class SK_API SkPerlinNoiseShader2 : public SkShader {
 public:
     struct StitchData;
     struct PaintingData;
 
     /**
-     *  About the noise types : the difference between the 2 is just minor tweaks to the algorithm,
-     *  they're not 2 entirely different noises. The output looks different, but once the noise is
-     *  generated in the [1, -1] range, the output is brought back in the [0, 1] range by doing :
+     *  About the noise types : the difference between the first 2 is just minor tweaks to the 
+     *  algorithm, they're not 2 entirely different noises. The output looks different, but once the 
+     *  noise is generated in the [1, -1] range, the output is brought back in the [0, 1] range by 
+     *  doing :
      *  kFractalNoise_Type : noise * 0.5 + 0.5
      *  kTurbulence_Type   : abs(noise)
      *  Very little differences between the 2 types, although you can tell the difference visually.
+     *  "Improved" is based on the Improved Perlin Noise algorithm described at
+     *  http://mrl.nyu.edu/~perlin/noise/. It is quite distinct from the other two, and the noise is
+     *  a 2D slice of a 3D noise texture. Minor changes to the Z coordinate will result in minor
+     *  changes to the noise, making it suitable for animated noise.
      */
     enum Type {
         kFractalNoise_Type,
         kTurbulence_Type,
+        kImprovedNoise_Type,
         kFirstType = kFractalNoise_Type,
-        kLastType = kTurbulence_Type
+        kLastType = kImprovedNoise_Type
     };
     /**
      *  This will construct Perlin noise of the given type (Fractal Noise or Turbulence).
      *
      *  Both base frequencies (X and Y) have a usual range of (0..1).
      *
      *  The number of octaves provided should be fairly small, although no limit is enforced.
      *  Each octave doubles the frequency, so 10 octaves would produce noise from
      *  baseFrequency * 1, * 2, * 4, ..., * 512, which quickly yields insignificantly small
      *  periods and resembles regular unstructured noise rather than Perlin noise.
      *
      *  If tileSize isn't NULL or an empty size, the tileSize parameter will be used to modify
      *  the frequencies so that the noise will be tileable for the given tile size. If tileSize
      *  is NULL or an empty size, the frequencies will be used as is without modification.
      */
     static SkShader* CreateFractalNoise(SkScalar baseFrequencyX, SkScalar baseFrequencyY,
                                         int numOctaves, SkScalar seed,
                                         const SkISize* tileSize = NULL);
     static SkShader* CreateTurbulence(SkScalar baseFrequencyX, SkScalar baseFrequencyY,
                                      int numOctaves, SkScalar seed,
                                      const SkISize* tileSize = NULL);
     /**
+     * Creates an Improved Perlin Noise shader. The z value is roughly equivalent to the seed of the
+     * other two types, but minor variations to z will only slightly change the noise.
+     */
+    static SkShader* CreateImprovedNoise(SkScalar baseFrequencyX, SkScalar baseFrequencyY,
+                                         int numOctaves, SkScalar z);
+    /**
      * Create alias for CreateTurbulunce until all Skia users changed
      * its code to use the new naming
      */
     static SkShader* CreateTubulence(SkScalar baseFrequencyX, SkScalar baseFrequencyY,
                                      int numOctaves, SkScalar seed,
                                      const SkISize* tileSize = NULL) {
     return CreateTurbulence(baseFrequencyX, baseFrequencyY, numOctaves, seed, tileSize);
     }
 
 
     size_t contextSize() const override;
 
     class PerlinNoiseShaderContext : public SkShader::Context {
     public:
-        PerlinNoiseShaderContext(const SkPerlinNoiseShader& shader, const ContextRec&);
+        PerlinNoiseShaderContext(const SkPerlinNoiseShader2& shader, const ContextRec&);
         virtual ~PerlinNoiseShaderContext();
 
         void shadeSpan(int x, int y, SkPMColor[], int count) override;
         void shadeSpan16(int x, int y, uint16_t[], int count) override;
 
     private:
         SkPMColor shade(const SkPoint& point, StitchData& stitchData) const;
         SkScalar calculateTurbulenceValueForPoint(
             int channel,
             StitchData& stitchData, const SkPoint& point) const;
+        SkScalar calculateImprovedNoiseValueForPoint(int channel, const SkPoint& point) const;
         SkScalar noise2D(int channel,
                          const StitchData& stitchData, const SkPoint& noiseVector) const;
 
         SkMatrix fMatrix;
         PaintingData* fPaintingData;
 
         typedef SkShader::Context INHERITED;
     };
 
 #if SK_SUPPORT_GPU
     const GrFragmentProcessor* asFragmentProcessor(GrContext* context, const SkMatrix& viewM,
                                                    const SkMatrix*, SkFilterQuality) const override;
 #endif
 
     SK_TO_STRING_OVERRIDE()
-    SK_DECLARE_PUBLIC_FLATTENABLE_DESERIALIZATION_PROCS(SkPerlinNoiseShader)
+    SK_DECLARE_PUBLIC_FLATTENABLE_DESERIALIZATION_PROCS(SkPerlinNoiseShader2)
 
 protected:
     void flatten(SkWriteBuffer&) const override;
     Context* onCreateContext(const ContextRec&, void* storage) const override;
 
 private:
-    SkPerlinNoiseShader(SkPerlinNoiseShader::Type type, SkScalar baseFrequencyX,
+    SkPerlinNoiseShader2(SkPerlinNoiseShader2::Type type, SkScalar baseFrequencyX,
                         SkScalar baseFrequencyY, int numOctaves, SkScalar seed,
                         const SkISize* tileSize);
-    virtual ~SkPerlinNoiseShader();
+    virtual ~SkPerlinNoiseShader2();
 
-    const SkPerlinNoiseShader::Type fType;
+    const SkPerlinNoiseShader2::Type fType;
     const SkScalar                  fBaseFrequencyX;
     const SkScalar                  fBaseFrequencyY;
     const int                       fNumOctaves;
     const SkScalar                  fSeed;
     const SkISize                   fTileSize;
     const bool                      fStitchTiles;
 
     typedef SkShader INHERITED;
 };
 
 #endif